This invention relates to an improvement in a support for winding yarn. The term "yarn" is intended herein to include textile yarns and other forms of yarns, e.g., industrial yarn, including monofilament and multifilament yarns with or without twist, interlacing or other entanglements, including threads. Such yarn supports are referred to sometimes by other names, such as bobbins, cores, spools and tubes.
Yarn supports are used daily in large quantities for winding packages of synthetic yarns at high speeds. Prior art supports are described, for example, in Heatherly U.S. Pat. No. 3,103,305, Sowell U.S. Pat. No. 3,284,023 and Sowell U.S. Pat. No. 3,794,260, all of which disclose yarn supports with a `string-up slot` for winding a `transfer tail`. Such yarn supports are conventionally made from an inexpensive compressible core material such as Kraft paper-board, with an external covering of water-resistant material, such as parchment paper, generally referred to as "parchment" in the trade. Conventionally, these yarn supports are made by spiral winding of the paperboard layers and the external covering to provide cylindrical stock in appropriate lengths, e.g. of about 3 meters, of the appropriate diameter and wall thickness, followed by cutting these lengths into sections according to the size required for the individual yarn supports.
It is important that yarn supports be available cheaply and yet within close dimensional specifications. They should be inexpensive because they are generally not reusable by synthetic yarn manufacturers. If they do not meet critical dimensional specifications, they will be unsuitable for use with high-speed machinery. Thus, it is important that both the internal diameter (ID) and the length be within a close tolerance to permit use of more than one support on a single spindle. The length of a support with a string-up slot should be within a close tolerance to give the precise length of transfer tail; as the speeds of yarn winding machinery increase, so even small changes in the length of the yarn support can cause large differences in the length of the transfer tail.
The yarn is normally unwound from the support over the end remote from the transfer tail. It is important to avoid snagging of the yarn as it passes over the end of the support, otherwise the yarn may break or at least contain a defect which will be revealed in the final fabric. Although the customary construction of yarn supports, as mentioned above, is low in cost and satisfactory in many respects, there have been complaints about existing designs because of the frequency of snagging.
It has been conventional practice to smooth the end of the yarn support, e.g. by burnishing with high pressure. Several methods for smoothing the ends of yarn supports are discussed in Dunlap U.S. Pat. No. 1,896,135. Burnishing is an easy, economic process which provides the possibility of carefully controlling the length of the support within a required tolerance. It is still, however, desired to improve the smoothness beyond what is possible by mere burnishing, so as to reduce the frequency of snagging. It has been attempted to increase the effectiveness of burnishing by first tapering the cut end of the yarn support, but this has not sufficiently reduced the amount of snagging.
The frequency of snagging has been sufficient to cause many processors to use plastic caps which slide over the end of the yarn support, and thus avoid the hazard. Although these caps reduce the problems of snags, they are an additional expense, and manpower must be provided to position and recover the caps at the beginning and end of each processing operation. It would be desirable to provide a yarn support which could be relied on to avoid snags without the necessity for using such a cap.
I believe that much of the snagging has been a result of deformation of the end of the support. Such deformation can occur during handling of cartons containing several layers of yarn packages, especially if moisture has been able to penetrate the paperboard core where it has not been protected by a water-resistant covering.